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Notes: Summary Neuromagnetic responses to different auditory stimuli (noise bursts and short speech stimuli) were mapped over both hemispheres of seven healthy subjects. The results indicate that a particular acoustic feature of speech, vowel onset after voice-less fricative consonants, evokes a prominent response in the human supratemporal auditory cortex. Although the observed response seems to be specific to acoustic rather than phonetic characteristics of the stimuli, it might reflect feature detection essential for further speech processing.

Notes: The spontaneous nuclear spin ordering in the simple diamagnetic metals Cu and Ag has been studied by neutron diffraction using the spin dependent part of the nuclear cross section. Simple antiferromagnetic ordering of type I has been found in zero field for these fcc-systems below 60 and 560 pK for Cu and Ag, respectively. The ordering in an applied field has been investigated and the phase diagrams have been determined: a very complex phase diagram with different magnetic structures, strong hysteresis, and time dependence was found for Cu, while in Ag the phase diagram is very simple. Comparison with ab initio calculations allows a rather deep insight into the interactions leading to the ordering. © 1996 American Institute of Physics.

Notes: Abstract We have constructed a rotating nuclear demagnetization cryostat and used it for continuous-wave NMR experiments on superfluid3He-A and3He-B. The measurements were performed in a long cylindrical geometry of 5 mm diameter, with the cylinder axis parallel to the axis of rotation and with the external magnetic field H0=284 or 142 Oe in the same direction. The angular velocity of rotation Ω was varied between 0.2 and 1.5 rad/sec, and the experiments were done under 29.3 bar pressure at temperatures between Tc=2.72 and about 1.4 mK. As a guide to the new and esoteric field of superfluid3He in rotation, we first review the general theory at some length in relatively simple terms. Pictorial explanations are often given. In3He-A, a rotation-dependent NMR satellite was found; its intensity a rotation-dependent NMR satellite peak was discovered; its relative intensity increases linearly with Ω. The position of the satellite is independent of Ω and H, and does not depend on whether the sample was cooled from the Fermi-liquid region to the A phase while rotating or at rest. At temperatures 0.1〈1−T/Tc〈0.3, the frequency shift of the satellite can be described by the parameter Rt=0.86−1.1(1−T/Tc). Cooldown under rotation produced systematically larger satellite intensities than cooldown at rest. A second, metastable satellite, best seen at rest and disappearing in less than 30 min, was also discovered. Furthermore, the main NMR peak broadens during rotation, while the total NMR absorption remains the same. The behavior of the rotation-dependent satellite strongly supports the existence of vortices in3He-A, their number being proportional to Ω; the satellite is caused by localized spin wave modes trapped by vortex cores. Theoretical calculations agree quite well with our experimental data if continuous vortices, without a singularity in the order parameter, are assumed. Their presence is also responsible for the additional broadening of the main peak, due either to increased spin diffusion or to scattering of spin waves. The metastable satellite is caused by textural boundaries, probably by twist solitons in the superfluid, created by the rapid cooldown of the sample. In3He-B, a series of nearly equally spaced NMR satellites was found on the high-frequency side of the main peak with the cryostat at rest. Under rotation the separation between the satellites increases linearly with Ω. The spacing displays a jump, proportional to Ω, at 1−T/Tc=0.40. The discontinuity occurred only during start/stop experiments, not if the cryostat was continuously rotated while warming over the transition region. Immediately after rotation had been started the whole NMR spectrum shifted toward higher frequencies for about 30 sec; these transients were seen only at Ω〉0.25 rad/sec. In3He-B, the order parameter is strongly influenced by the wall of the container, producing the so-called flareout texture, with the angle β between the $$\hat n$$ vector andH equal to 63° at the walls. The satellites can be explained as spin wave modes arising from an almost harmonic potential well formed by the $$\hat n$$ texture. The creation of vortices changes the texture and increases the steepness of the potential and therefore increases the satellite spacing during rotation. The vortices themselves perturb the $$\hat n$$ texture due to the long-range orientating effect of their cores on the order parameter. The discontinuity in the satellite splitting at 1−T/Tc=0.40 is explained as being due to a first-order phase change in the vortex core at this temperature. The transient shift in the NMR spectrum, immediately after the start of rotation when vortices are not yet present, is caused by the large superfluid vs. normal liquid counterflow; this phenomenon thus gives an estimate for the time needed to create vortices in3He-B.

Notes: Abstract Nuclear magnetism in metallic copper has been studied by demagnetizing highly polarized spins to low fields where spin-spin interactions dominate. In earlier experiments anomalous spin-lattice relaxation caused by impurities warmed up nuclear spins too fast; this adverse effect was overcome by selective oxidation of impurities. In zero field the critical temperatureT c of the antiferromagnetic transition is 58±10 nK, and during the first-order phase change the entropy increases from (0.48±0.03)ℛ ln 4 to (0.61±0.03)ℛ ln 4. The critical fieldB c =0.27±0.01 mT. The entropy and the static susceptibility of the nuclear spins were measured as a function of temperature whenB=0. These curves agree with theory in the paramagnetic state. In a polycrystalline sample two anomalies were observed at the lowest entropies in the NMR line shapes of the dynamic susceptibility and in the behavior of the static susceptibility. However, when measuring the static susceptibility of a single-crystal specimen in the three Cartesian directions, three different ordered phases were found. These antiferromagnetic states are described and theB-S phase diagram is presented. Metastability and nonadiabaticity are discussed. The observed large reduction ofT c from the mean field calculationT MF=230 nK is caused by fluctuations. The free electron model of the Ruderman-Kittel (RK) interaction seems to be able to explain only one ordered phase. However, relatively small changes to the RK range function or inclusion of non-s-electron-mediated interactions to the Hamiltonian may increase the number of ordered phases to three. Long-living metastable states are another possible explanation for the observations.

Notes: Abstract The Mössbauer resonance of the 21.6 keV transition in151Eu has been used to investigate the magnetic properties of divalent ionic europium compounds at ultra low temperatures. The specimens were cooled by a3He/4He dilution refrigerator to a minimum temperature of 0.04 K. The following magnetic ordering temperatures were found: EuSO4, 0.43 K; EuF2, 1.0 K; EuCO3, 1.05 K; EuCl2, 1.1 K; EuC2O4, 1.9 K; EuC2O4 · H2O, 2.8 K. The absolute value of the saturation hyperfine fieldH eff of all these compounds is between 315 and 337 kOe. The temperature dependence ofH eff deviates somewhat from aS=7/2 Brillouin function. This behavior is probably due to relaxation phenomena.

Notes: [Auszug] Experiments on vortices in rotating superfluid 3He have revealed phenomena which have not been observed in any other quantum liquid and have implications in fields beyond low-temperature physics. In 3He-A, vorticity may be supported by a continuous winding of the order ...

Notes: [Auszug] Black-and-white line drawings of everyday objects (for example, vase, book, cat) were presented to six healthy right-handed subjects (age 25-34 yr; 4 males) for 100ms once every 5 s, randomly to the lower quadrant of the left or right visual field. The subject first fixated on a point in the middle ...

Notes: Abstract The viscosity η of liquid 3 He has been measured along the melting curve from 1 to 100 mK by means of a vibrating wire viscometer. In the normal Fermiliquid region we find 1/ηT2 = 1.17−3.10T, where η is in ΜP and T in K. At the transition temperature T A = 2.6 mK a rapid decrease occurs in η n , the viscosity of the normal component. Within 0.3 mK below T A , η n decreases to about 25% of ηA, but then becomes essentially constant. In the B phase η n first decreases to 20% of ηA and then seems to increase below 1.4 mK. Data on ϱ n , the density of the normal component, are also presented in the A and B phases. The results show that viscous flow is accompanied by a flow of zero dissipation, thus proving superfluidity in the A and B phases. The viscosity data at magnetic fields up to 0.9T have been related to theoretical calculations of the energy gap of superfluid 3 He near T A . The splitting of the A transition and the suppression of the B phase in an external field were also measured.

Notes: Abstract Measurements of the melting curve of He3 have been made from 3 m° K to 40 m° K, after cooling the liquid-solid He3 mixture by the adiabatic solidification method. The slope of the melting curve shows that at the lowest temperature there is a substantial departure of the solid He3 entropy fromR ln 2. This effect is due to nuclear spin ordering. Temperatures below 3 m° K were obtained during compression. By theoretically estimating the melting curve below 3 m° K it is possible to estimate temperatures from pressure measurements. By such means it is estimated that Kelvin temperatures of 1.5 to 2 m° K were actually achieved.

Notes: Abstract The magnetic dipole interaction between the nuclear magnetic momentu and the hyperfine fieldH hf in ferromagnetic metals leads to well-defined, evenly spaced nuclear energy levels which are accurately measurable by NMR techniques. When this is combined with the well-established anisotropic γ-ray emission properties of radioactive nuclei an excellent basis for absolute temperature measurement between 1 and 30 mK is obtained. Practical applications, however, require consideration of several experimental aspects. These are discussed in detail and graphs and tables are given in such a form that the data can be easily utilized. Experience gained with a nuclear orientation thermometer system employed in a nuclear refrigeration cryostat is discussed. A calibration of a pulsed copper NMR thermometer against a54MnNi nuclear orientation thermometer is presented.